JP6528719B2 - Optical modulator with FPC and optical transmitter using the same - Google Patents

Description

  The present invention relates to an optical modulator and an optical transmitter, and more particularly to an optical modulator including an FPC (Flexible Printed Circuits) for inputting a high frequency signal, and an optical transmitter using the optical modulator.

In high-speed / high-capacity optical fiber communication systems, optical modulators incorporating waveguide-type optical modulation elements are often used. Among them, a light modulation element using LiNbO ₃ (hereinafter also referred to as LN) having an electro-optical effect as a substrate can realize a wide band light modulation characteristic with a small loss of light, and hence a high speed / large capacity optical fiber It is widely used in communication systems.

  In the light modulation element using this LN, various adjustments may be made to maintain the modulation characteristics of the Mach-Zehnder type optical waveguide, the RF electrode for applying a high frequency signal which is a modulation signal to the optical waveguide, and the waveguide well. And a bias electrode for performing. Then, these electrodes provided in the light modulation element are connected to an external electronic circuit via lead pins and a connector provided in the housing of the light modulator that accommodates the light modulation element.

  On the other hand, the modulation method in the optical fiber communication system receives a recent trend of increasing transmission capacity, and performs multi-level modulation such as QPSK (Quadrature Phase Shift Keying), DP-QPSK (Dual Polarization-Quadrature Phase Shift Keying), etc. A transmission format that incorporates polarization multiplexing into multilevel modulation is the mainstream.

  An optical modulator performing QPSK modulation (QPSK optical modulator) and an optical modulator performing DP-QPSK modulation (DP-QPSK optical modulator) are provided with a plurality of nested structure optical waveguides, and a plurality of high frequency signals. Since the signal electrode and the plurality of bias electrodes are provided (for example, see Patent Document 1), the size of the housing of the optical modulator tends to be increased, and the demand for miniaturization is particularly strong.

  As one measure to meet this demand for miniaturization, the push-on coaxial connector, which was conventionally provided in the housing of the optical modulator as an RF electrode interface, is replaced with a lead pin similar to the bias electrode interface. There has been proposed an optical modulator to which an FPC (Flexible Printed Circuits) (FPC) has been added for connecting the lead pins of the above to an external circuit board.

  For example, in the DP-QPSK optical modulator, an optical modulation element configured by four Mach-Zehnder optical waveguides each having an RF electrode is used. In this case, although the increase in size of the case can not be avoided by providing four push-on coaxial connectors in the case of the optical modulator, the use of lead pins and an FPC instead of the coaxial connector enables miniaturization. .

  In addition, since the lead pins of the light modulator housing and the circuit board on which the electronic circuit for causing the light modulator to perform the modulation operation is mounted are connected through the above-mentioned FPC, it is conventionally used It is not necessary to perform the extra length processing of the coaxial cable, and the mounting space of the optical modulator in the optical transmission apparatus can be reduced.

  The FPC used for the optical modulator is manufactured using, for example, a flexible polyimide base material as a substrate (hereinafter referred to as an FPC substrate), and each of a plurality of through holes provided near one end is a wiring It is electrically connected to each of the pads provided at the other end through the pattern. Then, a plurality of lead pins protruding from the bottom or side of the housing of the optical modulator are respectively inserted into the plurality of through holes, fixed by, for example, solder and electrically connected, and the plurality of pads are soldered to the circuit board. Fixed and connected by As a result, a high frequency signal provided from the pad on the circuit board is provided to the corresponding RF electrode of the light modulation element through the corresponding through hole and the lead pin, and high speed light modulation is performed.

  In the optical modulator using the above-described FPC, as described above, the housing can be miniaturized, and the mounting space of the optical modulator on the circuit board can be reduced, so that the optical transmitter can be miniaturized. It can contribute greatly.

  FIG. 9 is a view showing the configuration of a conventional light modulator provided with such an FPC, and FIG. 9 (a) is a top view of the light modulator, FIG. 9 (b) is a front view, FIG. 9 (c) Is a bottom view. The light modulator 900 includes a light modulation element 902, a housing 904 for housing the light modulation element 902, a flexible printed circuit (FPC) 906, an optical fiber 908 for entering light into the light modulation element 902, and light. And an optical fiber 910 for guiding the light output from the modulation element 902 to the outside of the housing 904.

  The housing 904 is provided with four lead pins 920, 922, 924, 926 respectively connected to four RF electrodes (not shown) of the light modulation element 902, and the lead pins 920, 922, 924, 926 are For example, through holes 1020, 1022, 1024, and 1026, which will be described later, provided in the FPC 906 are inserted and fixed by, for example, solder and electrically connected.

  FIG. 10 is a diagram showing the configuration of the FPC 906. As shown in FIG. FIG. 10A is a view showing the structure of one surface of the FPC 906 (for example, the surface shown in FIG. 9C, referred to as “front surface” here), and FIG. It is a figure which shows the structure of the other surface (it calls a "back side") of FPC906. In the front surface shown in FIG. 10A, four pads 1010, 1012, 1014, and 1016 are provided side by side along the direction of the one side 1000 in the vicinity of the one side 1000 on the lower side in the figure. There is. In addition, on the side of the other side 1002 opposite to the side 1000, four through holes 1020, 1022, 1024, 1026 are provided side by side along the direction of the side 1002, for example. Further, the four pads 1010 1012 1014 1016 are electrically connected to the through holes 1020 1022 1024 1026 by wiring patterns 1030 1032 1034 1036, respectively.

  On the other hand, on the back surface shown in FIG. 10B, a ground pattern 1040 (hatched portion in the figure) is formed. Also, in order to avoid electrical contact between the ground pattern 1040 and the through holes 1020, 1022, 1024, 1026, the conductors constituting the ground pattern 1040 have a circular shape around the through holes 1020, 1022, 1024, 1026. It has been removed.

  The wiring patterns 1030, 1032, 1034, and 1036 formed on the front surface shown in FIG. 10A are, for example, characteristic impedances because the ground pattern 1040 is formed on the back surface across the substrate of the FPC 906, for example. May be designed to be 50 Ω.

  Then, the four pads 1010, 1012, 1014, and 1016 are respectively fixed to the pads of the external circuit board by, for example, solder and electrically connected, thereby the RF of the light modulation element 902 included in the light modulator 900. The electrodes and the electronic circuit configured on the circuit board are electrically connected to drive the light modulator 900. Note that the shape of the FPC 906 is generally a horizontally long rectangle having a short side in the signal transmission direction as shown in the drawing so as to minimize the wiring pattern and suppress the microwave loss as low as possible. As described above, when four pads 1010, 1012, 1014, and 1016 are provided, they have a rectangular shape of about 20 mm or less in the long side direction and about 10 mm or less in the short side direction.

  FIG. 11 is a diagram showing an example of a state in which the light modulator 900 is connected to the circuit board on which the electronic circuit is configured, and FIG. 11 (a) is a top view direction of the light modulator 900 (shown in FIG. 9 (a)). Fig. 11 (b) is a cross-sectional view taken along the line BB in Fig. 11 (a), as viewed from the direction in which the surface can be seen. The description of the internal configuration of the optical modulator 900 is omitted in FIG.

  On the circuit board 1100, an electronic circuit including a drive circuit 1104 for driving the light modulation element 902 of the light modulator 900 is configured. The light modulator 900 and the circuit board 1100 are, for example, those of the light transmission apparatus. It is fixed to a base 1102 in the housing. As shown in FIG. 11A, the FPC 906 of the optical modulator 900 extends from the connecting portion with the lead pins 920, 922, 924, 926 to the left in the figure, and as shown in FIG. 11B, the left side. The end is bent in the diagonally lower left direction so as to contact the circuit board 1100, whereby the pads 1010 1012 1014 1016 of the FPC 906 are fixed to the pads 1110 1112 1114 1116 on the circuit board 1100 by, for example, solder. And electrically connected (FIG. 11 (a)).

  For connection between the ground pattern 1040 and the light modulator 900, for example, a ground lead pin (not shown) connected to the ground pattern formed on the light modulation element 902 is provided in the housing 904, Assuming that a hole (not shown) to be engaged with the ground lead pin is provided in the FPC 906, the ground lead pin may be inserted into the hole and soldered to the ground pattern 1040. Further, for connection between the ground pattern and the circuit board 1100, for example, a conductive pin (not shown) brazed to the ground pattern 1040 is provided on the FPC 906, and the conductive pin and the ground pattern on the circuit board 1100 And can be soldered together.

  In the optical modulator 900 having the above configuration, a wiring pattern 1030 having a predetermined characteristic impedance is provided between the drive circuit 1104 provided on the circuit board 1100 and the lead pins 920 922 924 and 926 of the optical modulator 900. , 1032, 1034 and 1036, respectively. Thus, in principle, the output impedance of the drive circuit 1104, the input impedance of the optical modulator 900, and the characteristic impedances of the wiring patterns 1030, 1032, 1034, and 1036 are matched (matched) in principle. A high frequency signal can be efficiently propagated from the circuit 1104 to the optical modulator 900.

  However, in practice, due to manufacturing variations of the FPC 906, etc., a mismatched portion of the impedance occurs in the high frequency signal path from the drive circuit 1104 to the light modulator 900, and reflection of the high frequency signal occurs due to the impedance mismatch. It can. Such an impedance mismatch is particularly likely to occur at the solder connection portions between the lead pins 920, 922, 924, and 926 provided on the housing 904 and the through holes 1020, 1022, 1024, and 1026 provided on the FPC 906. .

  That is, in general, the outer diameters of the lead pins 920, 922, 924, 926 and the inner diameters of the through holes 1020, 1022, 1024, 1026 are not always constant among products, and are manufactured with a certain dimensional tolerance. Therefore, at the solder connection between the lead pins 920, 922, 924, 926 and the through holes 1020, 1022, 1024, 1026, the outer surfaces of the lead pins 920, 922, 924, 926 and the through holes 1020, 1022, Variations in the distance between the inner surfaces 1024 and 1026, variations in the shape of the solder, and the like tend to cause impedance mismatch due to these variations.

  When such an impedance mismatch occurs, in the portion where the mismatch occurs, part of the power of the high-frequency signal passing through the portion is reflected in the direction opposite to the propagation direction, for example, incident on the output of the drive circuit 1104 Be done. As a result, the operation in the drive circuit 1104 becomes unstable, and in some cases, an unstable phenomenon such as noise occurs in the high frequency signal output from the drive circuit 1104, and the transmission quality of the optical system using the optical modulator 900 Problems can arise.

  From the above background, in an optical modulator provided with an FPC for making electrical connection with an external circuit board, the optical modulator can be appropriately selected even when reflection of high frequency signals occurs at the connection portion between the FPC and the optical modulator main body. It is desirable to realize a configuration that can be driven to maintain high optical transmission quality.

One aspect of the present invention is an optical modulator provided with a flexible wiring board that makes electrical connection with a circuit board. In the optical modulator, the flexible wiring board includes at least one wiring pattern for transmitting a high frequency signal, and the wiring pattern includes at least one high frequency attenuation unit for attenuating the power of the high frequency signal by a predetermined amount.
According to another aspect of the present invention, the high frequency attenuation portion is configured of a portion of the wiring pattern loaded with a high frequency attenuation film.
According to another aspect of the present invention, the high frequency attenuation film is made of a material containing carbon and / or ferrite.
According to another aspect of the present invention, the high frequency attenuation portion is a curved conductor pattern configured such that the propagation direction of the high frequency signal is bent to an angle of 90 degrees or more with a predetermined curvature.
According to another aspect of the present invention, the high frequency attenuation portion is a conductor pattern configured to bend the propagation direction of the high frequency signal to an angle of 90 degrees or more.
According to another aspect of the present invention, the flexible wiring board is provided with the wiring pattern on one side and a ground pattern on the other side, and the high frequency attenuation portion is provided on the one side. It is configured by removing a part of the conductor of the ground pattern of the other surface within a predetermined distance range from a part of the wiring pattern.
According to another aspect of the present invention, the part of the wiring pattern provided on the one surface is a bent portion of a conductor pattern constituting the wiring pattern.
According to another aspect of the present invention, the part of the wiring pattern provided on the one surface is curved such that the propagation direction of the high frequency signal is bent to an angle of 90 degrees or more with a predetermined curvature. It is a bent portion of the conductor pattern.
According to another aspect of the present invention, the part of the wiring pattern provided on the one surface is a bent portion of a conductor pattern configured to be bent to an angle of 90 degrees or more in the propagation direction of the high frequency signal. is there.
Another aspect of the present invention is an optical transmitter including any of the above optical modulators and an electronic circuit that outputs at least a high frequency signal for causing the optical modulator to perform modulation operation.

FIG. 1 is a diagram showing a configuration of an optical modulator according to a first embodiment of the present invention. It is a figure which shows the structure of FPC used for the light modulator shown in FIG. It is a figure which shows an example of the state which connected the optical modulator shown in FIG. 1 to the circuit board in which the electronic circuit was comprised. It is a figure which shows the 1st modification of FPC used for the light modulator shown in FIG. It is a figure which shows the 2nd modification of FPC used for the light modulator shown in FIG. It is a figure which shows the 3rd modification of FPC used for the light modulator shown in FIG. It is a figure which shows the 4th modification of FPC used for the light modulator shown in FIG. It is a figure which shows the structure of the optical communication apparatus which concerns on the 2nd Embodiment of this invention. It is a figure which shows the structure of the conventional light modulator. It is a figure which shows the structure of FPC used for the light modulator shown in FIG. It is a figure which shows an example of the state which connected the optical modulator shown in FIG. 9 to the circuit board in which the electronic circuit was comprised.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
First Embodiment
First, an optical modulator according to a first embodiment of the present invention will be described. FIG. 1 is a view showing the configuration of an optical modulator according to an embodiment of the present invention.
The present light modulator 100 is provided between the light modulation element 102, a housing 104 for housing the light modulation element 102, and lead pins 120, 122, 124, 26 (described later) provided on the housing 104 and an external circuit board. A flexible printed circuit (FPC) 106 for electrical connection, an optical fiber 108 for causing light to be incident on the light modulation element 102, an optical fiber 110 for guiding the light output from the light modulation element 102 to the outside of the housing 104 And.

  The light modulation element 102 includes, for example, four Mach-Zehnder optical waveguides provided on an LN substrate, and four high-frequency electrodes (RF electrodes provided on the Mach-Zehnder optical waveguides to modulate light waves propagating in the optical waveguides). And a DP-QPSK optical modulator. The two lights output from the light modulation element 102 are polarization-combined by, for example, a lens optical system, and are guided to the outside of the housing 104 through the optical fiber 110.

  The housing 104 includes four lead pins 120, 122, 124 and 126 connected to the four RF electrodes (not shown) of the light modulation element 102, respectively. The lead pins 120, 122, 124, 126 provided in the housing 104 are inserted into through holes 220, 222, 224, 226, described later, provided in the FPC 106, and the through holes 220, 222, 224, 226 and the lead pins 120, Between 122, 124 and 126, respectively, they are connected and fixed, for example, by solder.

  FIG. 2 is a diagram showing the configuration of the FPC 106. As shown in FIG. FIG. 2A is a view showing the configuration of one surface of the FPC 106 (the surface shown in FIG. 1C (referred to as “front surface”)), and FIG. FIG. 7 is a diagram showing the configuration of the surface of the lens (referred to as “back surface”).

  The FPC 106 is manufactured using, for example, a substrate whose main material is polyimide (hereinafter referred to as an FPC substrate). For example, the FPC 106 is configured to have a rectangular plan view. As described above in the description of the prior art, the shape of the FPC 906 is generally a horizontally long rectangle in order to minimize the wiring pattern and suppress the microwave loss. Therefore, in the present embodiment, the FPC 106 has a rectangular shape as in the FPC 906. However, the shape of the FPC 106 is not limited to this, and may be, for example, a substantially quadrilateral shape.

  In the vicinity of one side 200 on the lower side of the front surface of the FPC 106 shown in FIG. 2A, four pads 210, 212, 214, and 216 are provided side by side along the direction of the one side 200. It is done. In addition, on the side of the other side 202 opposite to the side 200, for example, four through holes 220, 222, 224, and 226 are provided side by side along the direction of the side 202. Furthermore, the four pads 210, 212, 214, 216 are electrically connected to the through holes 220, 222, 224, 226 by the wiring patterns 230, 232, 234, 236, respectively.

  As described above, the four through holes 220, 222, 224, 226 are connected to the four lead pins 120, 122, 124, 126 provided in the housing 104, respectively, and the electronic circuit provided on the external circuit board The pads 210, 212, 214, and 216 are electrically connected to the pads that form a part of (for example, by soldering), so that the high frequency signal output from the electronic circuit is transmitted through the FPC 106. It is applied to the RF electrode of the modulation element 102.

  As shown in FIG. 2B, on the back surface opposite to the front surface of the flexible wiring board 106 provided with the wiring patterns 230, 232, 234 and 236, the wiring patterns 230, 232, 234 and 236 on the front surface are provided. A ground pattern 240 (hatched portion in the figure) is provided so as to include the position corresponding to. Also, in order to avoid electrical contact between the ground pattern 240 and the through holes 220, 222, 224, 226, the conductors constituting the ground pattern 240 have a circular shape at the periphery of the through holes 220, 222, 224, 226. It has been removed.

  As described above, by providing the ground pattern 240 at a position facing the wiring patterns 230, 232, 234, and 236 with the FPC 106 sandwiching the substrate, the wiring patterns 230, 232, 234, and 236 can be formed as desired (for example, It can be designed to be a high frequency signal line having a characteristic impedance of 50 Ω.

  It should be noted that the ground patterns (not shown) are formed on the front surface so that the wiring patterns 230, 232, 234 and 236 may be known as signal lines for high frequency such as microstrip lines, coplanar lines, and grounded coplanar lines. ) May be provided.

  The size of the FPC 106 is, for example, the length of the long side direction (direction of the side 200) in order to minimize the microwave loss by shortening the wiring patterns 230, 232, 234, 236 as much as the conventional FPC 906 described above. The length in the short side direction (direction perpendicular to the side 200) may be about 10 mm or less.

  FIG. 3 is a diagram showing an example of a state in which the light modulator 100 is connected to a circuit board on which an electronic circuit is configured, and FIG. 3 (a) is a top view direction of the light modulator 100 (shown in FIG. 1 (a)). Fig. 3 (b) is a sectional view taken along the line AA in Fig. 3 (a), as viewed from the direction in which the surface is visible. In addition, description is abbreviate | omitted about the internal structure of the optical modulator 100 in FIG.3 (b).

  On the circuit board 300, an electronic circuit including a drive circuit 304 (for example, an IC (Integrated Circuit Integrated Circuit) in which the drive circuit is integrated) for driving the light modulation element 102 of the light modulator 100 is configured, The light modulator 100 and the circuit board 300 are fixed to, for example, a base 302 in a housing of the light transmission apparatus. As shown in FIG. 3A, the FPC 106 of the optical modulator 100 extends from the connecting portion with the lead pins 120, 122, 124, 126 to the left in the figure, and as shown in FIG. 3B, the left side. The end is bent diagonally to the lower left so that it contacts the circuit board 300, whereby the pads 210, 212, 214, 216 of the FPC 106 are fixed to the pads 310, 312, 314, 316 on the circuit board 300 by, for example, solder. And electrically connected (FIG. 3 (a)).

  For connection between the ground pattern 240 and the light modulator 100, for example, a ground lead pin (not shown) connected to the ground pattern formed on the light modulation element 102 is provided in the housing 104, Assuming that a hole (not shown) to be engaged with the ground lead pin is provided in the FPC 106, the ground lead pin may be inserted into the hole and soldered to the ground pattern 240. Further, for connection between the ground pattern 240 and the circuit board 300, for example, a conductor pin (not shown) brazed to the ground pattern 240 is provided on the FPC 106, and the conductor pin and the ground on the circuit board 300. It can be performed by soldering the pattern.

  In particular, in the optical modulator 100 according to the present embodiment, as shown in FIG. 2A, the wiring patterns 230, 232, 234, and 236, which are conductor patterns for propagating a high frequency signal, respectively have the power of the high frequency signal. The high-frequency attenuators 250, 252, 254, 256 (indicated by dotted lines forming a part of the wiring patterns 230, 232, 234, 236, respectively) for attenuating by a predetermined amount are provided. More specifically, the high frequency attenuation sections 250, 252, 254, 256 in the present embodiment respectively have the wiring patterns 230, 232, 234, 236 loaded with the high frequency attenuation film 260 made of a material containing carbon and / or ferrite. (Ie, the portions of the wiring patterns 230, 232, 234, 236 covered by the high frequency attenuation film 260).

  In the portions of the wiring patterns 230, 232, 234, 236 loaded with such a high frequency attenuation film 260, a part of the high frequency signal propagating through the wiring patterns 230, 232, 234, 236 is the high frequency attenuation film 260. Since it flows in and is consumed as heat, it functions as high frequency attenuation sections 250, 252, 254, 256 that attenuate the power of the high frequency signal by a predetermined amount (A (%)). The attenuation amount A of the high frequency signal power is adjusted by the size of the high frequency attenuation film 260 (thickness, distance along the length direction of the wiring patterns 230, 232, 234, 236 (the propagation direction of the high frequency signal)). Can.

  As a result, for example, the high frequency signal output from the drive circuit 304 is attenuated by the predetermined amount A (%) in the high frequency attenuators 250, 252, 254, and 256, respectively, and reaches the optical modulator 100. After passing through the attenuation units 250, 252, 254, 256, any position (for example, through holes 220, 222, 224, 226 and lead pins 120, 122) between the light modulation element 102 and an electrode (not shown). , 124, 126) passes through the high frequency attenuators 250, 252, 254, 256 again and is attenuated by a predetermined amount A (%) before being sent to the drive circuit 304. Since it reaches, the unstable phenomenon of the operation of the drive circuit 304 due to the reflection of the high frequency signal is prevented (or suppressed).

  As a result, the optical modulator 100 can be appropriately driven by the drive circuit 304 to maintain high optical transmission quality.

  In the present embodiment, one high frequency attenuation portion is provided for each of the wiring patterns 230, 232, 234, and 236, but the high frequency attenuation portions provided for each of these wiring patterns are not limited to one. , May be more than one.

  Further, in the present embodiment, the high frequency attenuation sections 250, 252, 254, 256 are respectively constituted by the portions of the wiring patterns 230, 232, 234, 236 in which the high frequency attenuation film 260 is loaded. The configuration is not limited as long as the high frequency is attenuated. In addition, it is desirable that such high frequency attenuation units 250, 252, 254, 256 attenuate the high frequency signal power by absorbing and / or diverging the high frequency signal power without reflecting it.

  Next, modifications of the present embodiment will be described using FIGS. 4 to 7. The FPCs described below can be used for the light modulator 100 in place of the FPCs 106, respectively.

First Modified Example
First, a first modification of the FPC 106 used in the light modulator 100 shown in FIG. 1 will be described.

  In the FPC 106 shown in FIG. 2, the high frequency attenuation sections 250, 252, 254, 256 are configured as portions of the wiring patterns 230, 232, 234, 236 on which the high frequency attenuation film 260 is loaded. On the other hand, in the present modification, the high-frequency attenuation portion is a curved conductor pattern configured to bend and / or bend with a predetermined curvature to an angle of 90 degrees or more in the propagation direction of the high-frequency signal. It consists of the part of.

  FIG. 4 is a view showing a configuration of an FPC 400 that can be used instead of the FPC 106 according to the present modification. FIG. 4A is a view showing the configuration of one surface of the FPC 400 (a surface (referred to as “front surface”) corresponding to the surface of the FPC 106 shown in FIG. 1C), and FIG. ) Is a figure which shows the structure of the other surface (it calls a "back side") of FPC400. In FIG. 4, the same components as those of the FPC 106 shown in FIG. 2 will be denoted by the same reference symbols as those in FIG. 2, and the description of FIG. 2 described above will be used.

  The FPC 400 shown in FIG. 4 has the same configuration as the FPC 106 shown in FIG. 2 but does not have the high-frequency attenuation film 260, and instead of the wiring patterns 230, 232, 234, 236, the wiring patterns 430, 432, 434, The difference is having 436.

  The wiring patterns 430, 432, 434 and 436 partially constitute high frequency attenuators 450, 452, 454, and 456, respectively. The high frequency attenuators 450, 452, 454, and 456 are for high frequency signals. It consists of two bends of the conductor pattern that changes the propagation direction by 90 degrees, and bends of a curved conductor pattern that changes the propagation direction of the high frequency signal by 180 degrees with a predetermined curvature. For example, the high frequency attenuation unit 450 has two bending portions 462 and 464 that change the propagation direction of the high frequency signal by 90 degrees, and a bending portion 466 that changes the propagation direction of the high frequency signal by 180 degrees with a predetermined curvature. . Further, on the back surface of the FPC 400, a ground pattern 440 (hatched portion in the figure) having the same configuration as the ground pattern 240 of the FPC 106 is formed.

  The high frequency signal propagating through the wiring pattern 430, which is a conductor pattern, leaks from the conductor pattern at a bending portion 462 or 464 or a bending portion 466 having a predetermined small curvature because of the straightness of the high frequency signal. The light is emitted and diverges (ie, part of the power of the high frequency signal propagating in the wiring pattern 430 in the guided mode is converted to the radiation mode in the bent portions 462 and 464 and / or the bent portion 466 and emitted to the air). As a result, the high frequency attenuation unit 450 functions as an attenuator that attenuates high frequency signal power by the amount of power diverged from the bending portions 462 and 464 and the bending portion 466 constituting the high frequency attenuation portion 450. Further, the amount of attenuation is desired depending on the magnitude of the angle of change of the propagation direction of the high frequency signal in the bent portions 462 and 464 and / or the curvature of the bent portion 466 and / or the magnitude of the change of the propagation direction of the high frequency signal. Can be adjusted or designed to the value of

  The other high frequency attenuators 452, 454, 456, as shown in FIG. 4, have the same configuration as that described above for the high frequency attenuator 450, so details of the configuration of the other high frequency attenuators and For the operation, the above description on the high frequency attenuation unit 450 is incorporated.

  In the present embodiment, the high-frequency attenuation units 450, 452, 454, and 456 are each configured by two bending portions and one bending portion, but the present invention is not limited to this, and the required attenuation amount Accordingly, at least one bend (that is, the bend of the conductor pattern) which bends the propagation direction of the high frequency signal to an angle of 90 degrees or more, and / or the angle of the propagation direction of the high frequency signal to 90 degrees or more with a predetermined curvature. It can be constituted by at least one bend (i.e., a bend of the conductor pattern) which changes up to.

Second Modified Example
Next, a second modification of the FPC 106 used for the light modulator 100 shown in FIG. 1 will be described.

  In this modification, the high frequency attenuation portion is a portion of the wiring pattern provided on the front surface of the FPC having the ground pattern provided on the rear surface and the distance to the portion on the rear surface where the ground pattern is not provided. Are made up of a portion which is a predetermined distance shorter than the other portions of the wiring pattern. Such a high frequency attenuation portion may be, for example, a portion of a ground pattern provided on the back surface of the FPC, in the vicinity of a portion of the wiring pattern provided on the front surface of the FPC (for example, the portion of the wiring pattern It can be configured by removing at a predetermined distance range from the position of. In addition, in order to facilitate understanding by avoiding redundant descriptions, in the description of the present modification, in the same manner as described above, some “nearby” means, for example, the part of “predetermined distance range” Shall be meant.

  FIG. 5 is a diagram showing a configuration of an FPC 500 that can be used instead of the FPC 106 according to the present modification. FIG. 5A is a view showing the configuration of one surface of the FPC 500 (a surface (referred to as “front surface”) corresponding to the surface of the FPC 106 shown in FIG. 1C), and FIG. ) Is a figure which shows the structure of the other surface (it calls "the back surface") of FPC500. In FIG. 5, the same components as those of the FPC 106 shown in FIG. 2 will be denoted by the same reference symbols as those in FIG. 2, and the description of FIG. 2 described above will be used.

  The FPC 500 shown in FIG. 5 has the same configuration as the FPC 106 shown in FIG. 2 but does not have the high frequency attenuation film 260 (FIG. 5A), and a ground pattern 540 (hatched portion shown) instead of the ground pattern 240. In that they have a) (FIG. 5 (b)). In FIG. 5A showing the front surface of the FPC 500, a ground pattern 540 provided on the back surface (FIG. 5B) of the FPC 500 and a wiring pattern provided on the front surface (FIG. 5A) In order to clarify the positional relationship with 230, 232, 234 and 236, a ground pattern 540 provided on the back surface is shown as a hatched portion surrounded by a dotted line. In addition, since the said part is the shape which saw through the back surface through the front surface, the illustration right and left is reverse with respect to the shape of the ground pattern 540 on the back surface shown to FIG. 5B.

  The ground pattern 540 provided on the back surface of the FPC 500 has conductor removing portions 560, 562, 564, 566 from which the conductor constituting the ground pattern 540 is removed. The conductor removing portions 560, 562, 564, 566 extend to the vicinity of the bent portions of the wiring patterns 230, 232, 234, 236 on the front surface, respectively.

  As a result, since the conductor of the ground pattern 540 on the back surface is removed in the vicinity of the bent portion of the wiring patterns 230, 232, 234, 236, the bent portion of the high frequency signal propagating in the bent portion Will weaken the strength of As a result, a part of the high frequency signal propagating in the waveguide mode in the bend portion is converted into a radiation mode and radiated into the air. That is, each of the bent portions of the wiring patterns 230, 232, 234, 236 where the conductors of the ground pattern 540 are removed in the vicinity thereof by the conductor removing portions 560, 562, 564, 566 radiates a part of high frequency signal power. The high-frequency attenuators 550, 552, 554, 556 are configured to perform attenuation.

  In the present embodiment, as shown in FIG. 5, the conductor of the ground pattern 540 near the bent portions of the wiring patterns 230, 232, 234, 236 is removed, but the present invention is not limited to this. , 232, 234, 236 may be removed from the conductor of the ground pattern 540 in the vicinity of the straight portions. Also in this case, the strength of confinement of the high frequency signal propagating in the linear portion is reduced, and a part of the power of the high frequency signal propagating in the guided mode is emitted into the air as a radiation mode to reduce the linear portion. The power of the propagating high frequency signal can be attenuated.

  Further, as shown in FIG. 5, the conductor removing portions 560, 562, 564, 566 of the ground pattern 540 are extended to the vicinity of the bent portions of the wiring patterns 230, 232, 234, 236 to make high frequency attenuation portions 550, 552, In addition to the components 554 and 556, the conductor removal portion of the ground pattern 540 may be extended to just under the bent portions of the wiring patterns 230, 232, 234 and 236 with the substrate of the FPC 500 interposed therebetween to constitute a high frequency attenuation portion . Also in this case, the high frequency signal propagating through the wiring pattern can be attenuated by weakening the confinement of the high frequency signal in the high frequency attenuation section and diverging a part of the power of the high frequency signal into the air as a radiation mode.

  Furthermore, in the present embodiment, the ground pattern is provided only on the back surface where the wiring pattern 230 and the like are not provided. However, the present invention is not limited to this, and the ground pattern may be provided on the front surface where the wiring pattern 230 and the like are provided. It can be In this case, instead of or in addition to the conductor removing portions 560, 562, 564, 566 being provided on the ground pattern 540 on the back surface, it is provided on the front surface in the vicinity of a part of the wiring pattern 230 etc. A part of the conductor of the ground pattern may be removed to constitute the high frequency attenuation part. As described above, even when a part of the conductor of the ground pattern provided on the front surface is removed in the vicinity of a part of the wiring pattern 230 or the like, the wiring pattern 230 or the like is the same as in the present modification shown in FIG. It is possible to weaken the confinement of the high frequency signal in a part of the power source and to dissipate the power of the part of the high frequency signal to the air as a radiation mode to attenuate the power of the high frequency signal propagating through the wiring pattern 230 or the like.

Third Modified Example
Next, a third modification of the FPC 106 used for the light modulator 100 shown in FIG. 1 will be described.

  In this modification, in the FPC 400 according to the first modification, as in the FPC 500 according to the second modification, the high-frequency attenuation portion is configured by partially removing the conductor of the ground pattern on the back surface. . That is, a part of the conductor of the ground pattern in the vicinity of the bent portion and / or the bent portion of the conductor pattern configured such that the propagation direction of the high frequency signal bends to an angle of 90 degrees or more and / or bends with a predetermined curvature. The high frequency attenuation unit is configured by removing the

  FIG. 6 is a view showing a configuration of an FPC 600 that can be used instead of the FPC 106 according to the present modification. FIG. 6A is a diagram showing the configuration of one surface of the FPC 600 (a surface (referred to as “front surface”) corresponding to the surface of the FPC 106 shown in FIG. 1C), and FIG. ) Is a figure which shows the structure of the other surface (it calls a "back side") of FPC600. 6, the same components as those of FPC 106 or FPC 400 shown in FIG. 2 or 4 are denoted by the same reference numerals as those in FIG. 2 or 4 and the description of FIG. 2 or 4 described above is used. Do.

  The FPC 600 shown in FIG. 6 has a configuration similar to that of the FPC 400 shown in FIG. 4 except that a ground pattern 640 (hatched portion shown) is provided instead of the ground pattern 440 (FIG. 6 (b)). Also, it differs in that high frequency attenuators 650, 652, 654, 656 are provided instead of the high frequency attenuators 450, 452, 454, 456. In FIG. 6A showing the front surface of the FPC 600, a ground pattern 640 provided on the back surface of the FPC 600 (FIG. 6B) and a wiring pattern provided on the front surface (FIG. 6A). In order to clarify the positional relationship with 430, 432, 434, 436, a ground pattern 640 provided on the back surface is shown as a hatched portion surrounded by a dotted line. In addition, since the said part is the shape which saw through the back surface through the front surface, the illustration right and left is reverse with respect to the shape of the ground pattern 640 on the back surface shown to FIG. 6B.

  The ground pattern 640 provided on the back surface of the FPC 600 has conductor removing portions 660, 662, 664, 666 from which the conductor forming the ground pattern 640 has been removed. The conductor removing portions 660 662 664, and 666 extend to the vicinity of the 180-degree bending portion of the wiring patterns 430, 432, 434, and 436 on the front surface, for example (for example, the bending portion of the wiring pattern 430). The conductor removing portion 660 extends to the vicinity of 466).

  Then, the high-frequency attenuators 650, 652, 654, 656 are the same as the high-frequency attenuators 450, 452, 454, 456 in the first modification, respectively, 2 of the conductor pattern for changing the propagation direction of the high-frequency signal by 90 degrees. Two bends (for example, bends 462 and 464 of the wiring pattern 430) and a 180 ° bend of the conductor pattern (for example, the bend 466 of the wiring pattern 430) which changes the propagation direction of the high frequency signal by 180 degrees with a predetermined curvature. And a conductor removing portion 660, 662, 664, 666 in the vicinity of the bend.

  As a result, since the conductor of the ground pattern 640 on the back surface is removed in the vicinity of the 180-degree bend of the wiring patterns 430, 432, 434, 436, the inside of the bend of the high-frequency signal propagating in the bend is Since the strength of confinement in the light source is weakened and a part of the power of the high frequency signal is dissipated into the air, the amount of attenuation of high frequency signal power in the high frequency attenuators 650, 652, 654, 656 is It becomes larger than the high frequency attenuation parts 450, 452, 454, and 456 according to the first modification.

  In the present embodiment, as shown in FIG. 6, the conductor of the ground pattern 640 in the vicinity of the 180-degree bent portion (for example, the bent portion 466 of the wiring pattern 430) of the wiring patterns 430, 432, 434, 436 is removed. However, the present invention is not limited thereto, and the conductor of the ground pattern 640 in the vicinity of at least one bent portion of the wiring patterns 430, 432, 434, 436 (for example, the bent portion 462 or 464 of the wiring pattern 430) may be removed. , And the same effect as described above can be obtained.

Fourth Modified Example
Next, a fourth modification of the FPC 106 used in the light modulator 100 shown in FIG. 1 will be described.

  In this modification, each wiring pattern is provided with a bending portion that changes the propagation direction of the high frequency signal by 90 degrees and / or a plurality of bending portions that changes the propagation direction of the high frequency signal by 180 degrees with a predetermined curvature. Constitute a high frequency attenuation unit.

  FIG. 7 is a diagram showing a configuration of an FPC 700 that can be used instead of the FPC 106 according to the present modification. FIG. 7A is a view showing the configuration of one surface of the FPC 700 (a surface (referred to as “front surface”) corresponding to the surface of the FPC 106 shown in FIG. 1C), and FIG. ) Is a figure which shows the structure of the other surface (it calls a "back side") of FPC700. 7, the same reference numerals as those in FIG. 2 are used for the same components as the FPC 106 shown in FIG. 2, and the description of FIG. 2 described above is used.

  The FPC 400 shown in FIG. 7 has the same configuration as the FPC 106 shown in FIG. 2 but does not have the high frequency attenuation film 260, and instead of the wiring patterns 230, 232, 234, 236, the wiring patterns 730, 732, 734, It differs in having 736.

  The wiring pattern 730 has four high frequency attenuation portions 750, 752, 754, and 756 configured by bending portions that change the propagation direction of the high frequency signal by 90 degrees. The wiring pattern 732 has a predetermined curvature and a high-frequency attenuation portion 760 formed of a bent portion that changes the propagation direction of the high-frequency signal by 180 degrees, and the predetermined curvature makes the propagation direction of the high-frequency signal 90 degrees or more The high-frequency attenuators 762, 764, 766, and 768 are formed of bent portions to be changed by

  Thus, the wiring patterns 730 and 732 can be through holes 220, 222, 224 and 226 and lead pins 120 and 122, respectively, by the plurality of high frequency attenuators 750, 752, 754, 756 and 760, 762, 764, 766 and 768, respectively. , 124, 126, and effectively reduce the power of the high frequency signal reflected at the solder connection with the electric circuit 124 (for example, the drive circuit 304) to drive the optical modulator 100. It is possible to prevent the occurrence of the instability phenomenon and realize stable driving of the optical modulator 100.

  As shown in FIG. 7, the wiring pattern 734 has line symmetry with the wiring pattern 732 to have the same configuration as that of the wiring pattern 732, and has the same function as the wiring pattern 732. The wiring pattern 736 has line symmetry with the wiring pattern 730 to have the same configuration as the wiring pattern 730, and has the same function as the wiring pattern 7320. Therefore, with regard to the configuration and operation of the wiring patterns 734 and 736, the description of the configuration and operation of the wiring patterns 732 and 730 described above is incorporated.

Second Embodiment
Next, a second embodiment of the present invention will be described. The present embodiment is an optical transmission device on which the optical modulator 100 (including one using the FPC according to any of the modifications shown in FIGS. 4 to 7) shown in the first embodiment is mounted.

  FIG. 8 is a diagram showing the configuration of the optical transmission apparatus according to the present embodiment. The present optical transmission apparatus 800 includes an optical modulator 802, a light source 804 that causes light to enter the optical modulator 802, a modulation signal generation unit 806, and a modulation data generation unit 808.

  The light modulator 802 is the light modulator 100 shown in FIG. 1 (in place of the FPC 106, any of FPCs 400, 500, 600, 700 shown in FIGS. 4 to 7 may be provided). The modulation data generation unit 808 receives transmission data given from the outside, generates modulation data (for example, data obtained by converting or processing transmission data into a predetermined data format) for transmitting the transmission data, and The generated modulation data is output to the modulation signal generation unit 806.

  The modulation signal generation unit 806 is an electronic circuit including a drive circuit (for example, the drive circuit 304) for outputting an electric signal for causing the light modulator 802 to perform the modulation operation, and the modulation data generation unit 808 outputs the modulation data Based on this, the modulation signal which is a high frequency signal for causing the light modulator 802 to perform the light modulation operation according to the modulation data is generated and input to the light modulator 100. The modulation signal consists of four RF signals corresponding to four RF electrodes (not shown) of the light modulation element 102 provided in the light modulator 100.

  The four RF signals are respectively input to the pads 210, 212, 214, and 216 of the FPC 106 (which may be any of the above-described variations of the FPC 106 as described above) of the light modulator 100, and a wiring pattern 230, 232, 234, 236, through holes 220, 222, 224, 226, and lead pins 120, 122, 124, 126, respectively.

  Accordingly, the light output from the light source 804 is modulated by the light modulator 100 and is output as the modulated light from the light transmitting apparatus 800.

  In particular, in the present optical transmission apparatus 800, since the optical modulator 100 having the above-described configuration is used as the optical modulator 802, the connection between the through hole 220 or the like of the FPC 106 or the like included in the optical modulator 100 and the lead pin 120 or the like of the housing 104 Even when the reflection of the high frequency signal occurs in the part, the power of the high frequency signal flowing back to the modulation signal generation unit 806 is effectively reduced to prevent the occurrence of the unstable operation of the modulation signal generation unit 806, and The drive quality can be maintained high by appropriately driving.

  100, 802, 900 ... light modulator, 102, 902 ... light modulation element, 104 ... housing 106, 400, 500, 600, 700, 906 ... FPC, 108, 110, 908, 910 ... optical fiber 120, 122, 124, 126, 920, 922, 924, 926 ... lead pin, 200, 202, 204, 206, 1000, 1002, 1004, 1006 ... side, 210, 212 , 214, 216, 310, 312, 314, 316, 1010, 1012, 1014, 1016, 1110, 1112, 1114, 1116 ... pads 220, 222, 224, 226, 1020, 1022, 1024, 1026. Through holes 230, 232, 234, 236, 430, 432, 434, 436, 30, 732, 734, 736, 1030, 1032, 1034, 1036 ... wiring pattern, 240, 440, 540, 640, 740, 1040 ... ground pattern, 250, 252, 254, 256, 450, 452, 454, 456, 550, 552, 554, 554, 556, 650, 652, 654, 656, 750, 752, 754, 756, 762, 764, 766, 768 ... high frequency attenuator, 260 ... high frequency attenuation Membrane, 300, 1100 ... circuit board, 302, 1102 ... base, 304, 1104 ... drive circuit, 462, 464 ... bent portion, 466 ... bent portion, 560, 562, 564, 566, 660, 662, 664, 666 ... conductor removing part, 800 ... light transmitting device, 804 ... Source, 806 ... modulation signal generating section, 808 ... modulation data generating unit.

Claims (5)

An optical modulator comprising a flexible wiring board for making an electrical connection with a circuit board, comprising:
A plurality comprises housings each to a plurality of electrodes connected pins of the light modulation element contained therein,
The flexible wiring board is provided with a plurality of wiring patterns connected to the pins to propagate a high frequency signal to the pins, and the wiring pattern is provided on one surface and faces the wiring pattern on the other surface. The ground pattern is provided in the part,
In all the wiring patterns provided on the flexible wiring board, a part of the conductor of the ground pattern of the other surface within a predetermined distance range from a part of the wiring pattern provided on the one surface is removed by, said some high-frequency signal propagated to diverge than other portions provide additional losses in the high frequency signal, high frequency attenuation portion is provided,
Light modulator. The part of the wiring pattern provided on the one surface is a bent portion of a conductor pattern that constitutes the wiring pattern.
The light modulator according to claim 1 . The part of the wiring pattern provided on the one surface is a curved portion of a curved conductor pattern configured such that the propagation direction of the high frequency signal is bent to an angle of 90 degrees or more with a predetermined curvature.
The light modulator according to claim 1 . The part of the wiring pattern provided on the one surface is a bent portion of a conductor pattern configured to be bent to an angle of 90 degrees or more in a propagation direction of a high frequency signal.
The light modulator according to claim 1 . An optical modulator according to any one of claims 1 to 4 ;
At least an electronic circuit for outputting a high frequency signal for causing the optical modulator to perform modulation operation;
Equipped with
Optical transmitter.

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